Fermentation: The process by which glucose is completely oxidized in absence of oxygen, to form alcohol or lactic acid and a small amount of energy is said to be fermentation. This process is followed in the field of industries, such as- bread factories, wine industries etc.

Anaerobic respiration occurs in some yeasts and bacteria and in muscle when exercise is strenuous and there is not enough oxygen. The first step in is glycolysis, the second is the citric acid cycle and the third is the electron transport system.

Differences between anaerobic respiration and fermentation

Anaerobic Respiration

It occurs within the cells

In this case, different enzymes formed within the cells take part directly in the reaction

In this case, the internal glucose of the cells is used.

It uses molecules other than oxygen to complete the metabolic cycle.

It exists mostly in bacteria, including the bacteria in many animal intestinal tracts.

Fermentation

It occurs outside the cells

In this case, different enzymes formed within the cells secrete out of the cells and take part in the reaction.

In this case, the external glucose is used.

It extends glycolysis, the first stage of metabolism, to produce usable energy

It is an extremely common way of gaining energy from food in the absence of sufficient oxygen.